import java.util.List;

/**
 * @author ghp
 * @date 2023/6/17
 * @title
 * @description
 */
public class Main {
    public static void main(String[] args) {
        Solution solution = new Solution();
        TreeNode root = new TreeNode(1);
        TreeNode r = new TreeNode(2);
        TreeNode rl = new TreeNode(3);
        root.right = r;
        r.left = rl;
        List<Integer> list = solution.preorderTraversal(root);
        list.forEach(System.out::println);
    }
}
